1. Field of the Invention
The present invention concerns a printed material manufactured by using a printing apparatus such as a letterpress printer or an ink jetting apparatus. Such a printed material includes, for example, an organic electroluminescence device, and an organic light emitting layer of the organic EL device is formed by using a printing apparatus such as a letterpress printer. Further, the printed material also includes, for example, a color filter, and a coloring layer thereof is formed by using the printing apparatus. In addition, the printed material also includes, for example, circuit substrates, thin film transistors, micro-lenses, and biochips.
2. Description of the Related Art
For example, various studies have been made on the method of forming an organic light emitting layer of an organic electroluminescence device (hereinafter referred to as an “Organic EL device”) and, as typical methods, various printing methods such as a photolithographic system, letterpress printing system, and ink jetting system have been known. In the formation of a pixel pattern of the organic EL device by the photolithographic system, a coating film of photosensitive resin layers for respective colors is formed over the entire substrate, and exposed patternwise, and then unnecessary portion of the coating film is removed to form each of pixels with the remaining pattern. In this method, since most of the coating film is removed by development, a great amount of material is lost. Further, since exposure and developing steps are conducted on every pixel, the number of steps increases. The photolithographic system is utilized for the manufacture not only for the organic EL device but also for various optical devices such as color filters and electric devices.
Then, the problem described above in the photolithographic system has become remarkable along with increase of the size of substrates to result in problems both in view of the cost and the environment. As a method of overcoming the problems, a system of manufacturing an optical device by a printing system has attracted attention. For example, in a case of manufacturing an organic EL device by the printing method, inks containing organic light emitting materials of R, G, B tri-colors are used and respective colors can be printed simultaneously by a step for once. Accordingly, when compared with the photolithography, since the ink material is scarcely lost wastefully and the step of forming three-color pixels can be shortened, decrease of the environmental burden and remarkable reduction of the cost can be expected.
As described above, since the printing system can simplify the manufacturing process and save the cost, the system is applied to the manufacture of optical devices such as organic EL devices or color filters. However, one of the problems in the printing system is “color mixing” and “blanking”. Description is to be made to a case of manufacturing the optical devices for letterpress printing as an example.
“Color mixing” means a failure in which inks are mixed to each other between adjacent pixels and coloring inks of different colors are mixed with each other. Coloring mixing is caused by the overflow of printed (jetted) ink exceeding a partition wall. In order to overcome the problem, JP-A No. Hei 5-93808 (Patent Document 1) proposes, for example, a method of manufacturing a color filter by using a printing system. JP-A Nos. Hei 7-248413 and 2003-243163 (Patent Documents 2 and 3) describe that a black resin layer incorporated with an ink repellent agent such as a fluoro-containing compound to form a partition wall in order to prevent ink bleeding and color mixing in the ink printing step.
“Blanking” is a failure mainly attributable to that an ink applied by a printing print or an ink jetting apparatus can not be diffused sufficiently and uniformly in a region surrounded with a partition wall, which causes display failure such as color shading or lowering of the contrast in the color filter, and pin holes causing short circuit in the organic EL device. Blanking occurs in a case where an ink repellent agent exudes from the lateral surface of the partition wall. Exudation of the ink repellent agent from the lateral surface of the partition wall is promoted by heating. Referring to FIG. 1, in a case of forming a partition wall by a photolithographic method, after coating a resin composition 20 as a partition wall to a substrate 10 (FIG. 1A), and exposing and developing the same by using a mask (FIGS. 1B, 1C), the partition wall is heated (post-baked). In this case, an ink repellent agent exudes from a portion of the partition wall as shown in FIG. 1D and an ink 41 applied by the printing apparatus does not spread by wetting to cause blanking (FIG. 1E).
Further, in a case of manufacturing a partition wall by the photolithographic system, by applying a photosensitive composition containing an ink repellent agent on a substrate and exposing and developing the same to form a partition wall, blanking occurs also in a case where the ink repellent agent is present in the opening of the partition wall is not removed sufficiently by a developer and the ink repellent agent remains within the pixel (FIG. 2A to FIG. 2E).
A typical method of manufacturing an optical device by using a letterpress printer is to be described according to the Patent Documents 2 and 3. The Patent Documents 2 and 3 describe a method of using a fluoro-containing material as an ink repellent agent for a partition wall of a color filter or an organic EL device manufactured by a printing system. Further, typical methods of manufacturing optical devices by using an ink jetting apparatus is to be described according to JP-A Nos. Hei 6-347637, 7-35915, 7-35916, 7-35917, and 9-203803 (in columns 0030 to 0035) (Patent Documents 4 to 8). The Patent Documents 4 to 7 describe methods of using fluoro-containing materials as the ink repellent agent for the partition wall of the color filter manufactured by the ink jetting method.
According to the methods described above, while color mixing by the printing could be prevented, since resin molecules of the ink repellent agent contained fluorine atoms entirely, the polarity for the entire resin molecules was high and compatibility with other resin ingredients and the solvent ingredient contained in the ink was low. Therefore, in the step of heat-baking after the exposure and development of the partition wall pattern, the ink repellent agent exuded from the partition wall to the pixel to cause the problem of “blanking”. Further, even when the partition wall was formed by using the ink repellent agent, since the ink repellent ingredient was not concentrated to the surface of the partition wall but the ink repellent molecules were dispersed, no sufficient ink repellency could be obtained to sometime result in “color mixing”, they cannot be said to sufficiently overcome the problem of “color mixing”.
For closely adhering the ink repellent agent to the partition wall thereby preventing exudation into the pixel and keeping a sufficient ink repellency at the same time, it has been proposed a method of using a compound as an ink repellent agent, having a resin compatible alkyl group on one side and an ink repellent perfluoroalkyl group on the opposite side thereby providing the ink repellency only on one side of the molecular chain (Patent Document 8).
However, even by the use of the compound of a structure in which a molecular chain having the resin compatibility and a molecular chain having the ink repellency are connected as the ink repellent agent, the ink repellent agent easily exudes from the lateral surface of the partition wall and the problem of “blanking” could not be solved.
The present invention has been achieved for overcoming the problems described above and intends to provide a printed material of high quality and high reliability by preventing color mixing and blanking upon manufacture of a printed material at a reduced cost by a simple process utilizing a printing system, as well as provide a manufacturing method thereof.